of Bt Corn on Rhizospheric and Soil Eubacterial Communities
and on Beneficial Mycorrhizal Symbiosis in Experimental
M. Castaldini,1 A. Turrini,2
C. Sbrana,3 A. Benedetti,4 M.
Marchionni,4 S. Mocali,4 A.
Fabiani,1 S. Landi,1 F. Santomassimo,1
B. Pietrangeli,5 M. P. Nuti,2,3
N. Miclaus,1 and M. Giovannetti,2,3*
Dipartimento di Biologia della Piante Agrarie,
Universita` di Pisa, Via del Borghetto 80, 56124 Pisa,
A polyphasic approach has been developed
to gain knowledge of suitable key indicators for the
evaluation of environmental impact of genetically
modified Bt 11 and Bt 176 corn lines on soil ecosystems.
We assessed the effects of Bt corn (which constitutively
expresses the insecticidal toxin from Bacillus
thuringiensis, encoded by the truncated Cry1Ab
gene) and non-Bt corn plants and their residues on
rhizospheric and bulk soil eubacterial communities
by means of denaturing gradient gel electrophoresis
analyses of 16S rRNA genes, on the nontarget mycorrhizal
symbiont Glomus mosseae, and on soil respiration.
Microcosm experiments showed differences in rhizospheric
eubacterial communities associated with the three
corn lines and a significantly lower level of mycorrhizal
colonization in Bt 176 corn roots. In greenhouse experiments,
differences between Bt and non-Bt corn plants were
detected in rhizospheric eubacterial communities (both
total and active), in culturable rhizospheric heterotrophic
bacteria, and in mycorrhizal colonization. Plant residues
of transgenic plants, plowed under at harvest and
kept mixed with soil for up to 4 months, affected
soil respiration, bacterial communities, and mycorrhizal
establishment by indigenous endophytes. The multimodal
approach utilized in our work may be applied in long-term
field studies aimed at monitoring the real hazard
of genetically modified crops and their residues on
nontarget soil microbial communities.
mosseae,Cry1Ab gene,Streptomyces spp,Brassica
napus,microorganisms,Porcellio scaber,soil microbial,crops.